That article from 2008 is still fairly accurate to the team of now 9 designers at Basecamp in 2014. Some thoughts to further this, though.

The aesthetic of Basecamp Classic and our older apps were simpler, then. That means there wasn’t much need to use Photoshop to change a hundred boxes from light grey to dark grey when you can do one global change from #CCC to #333 and hit refresh.

Every designer writes HTML, CSS, and to many extents, Ruby and CoffeeScript Because these are our shared languages from designer to programmer and back again, we find it easier to work on the actual Basecamp codebase and collaborate using Basecamp and GitHub faster than sending raster images. In fact, working with programmers has helped all of the designers become better at code, and vice versa designers helping programmers have a keener eye for design. We really value teaching each other.

Working in code is easier for product design than marketing design. Because applications need to have a consistent visual language, re-inventing and exploring this isn’t as necessary. Great UI is consistent and familiar, so there’s no need to change these on users. So, I still whip out Illustrator and Photoshop to do rough tests and quick sketches for marketing related work. You can see how much I used Illustrator in the visual exploration and typography behind redesigning Signal v. Noise.